Friday Philosophicals run most Fridays by Zoom (check the schedule). Seminars start at 3:30 pm and are expected to end by 4:20 pm.
April 16, 2021
Boreal peatlands are important ecosystems for carbon cycling, storing 1/3 of the world’s terrestrial carbon in only ~3% of the globe, making them a key mitigation strategy in global climate warming. Experimental warming has shown to affect plant and microbial communities in ways that potentially shift peatlands from carbon sinks to sources. The soil food webs including the microarthropod community are key in carbon cycling, but are relatively understudied in both peatlands and under experimental warming. My research capitalized on a large-scale experimental warming manipulation in two peatland sites in Northern Ontario, and addresses: 1) factors that drive litter decomposition and oribatid mite communities by examining different microhabitats 2) how these communities shift under experimental warming, and 3) the diversity of oribatid mites in Canadian peatlands. I show that peatland oribatid mite communities are driven by soil moisture and temperature, and that responses to warming are species- and site- specific. My synthesis of oribatids in Canadian peatlands updates the records from 71 to 186 species. My research also discusses the role of peatland microarthropods and their relation to ecosystem processes under environmental changes, as it is the first to link changes in soil biodiversity to peatland carbon storage and release.
Organisms regularly adjust their physiology to respond to predictable seasonal or environmental variation. Annual cycle transitions could be disrupted by contaminants (e.g., methylmercury) or stressors (e.g., inclement weather, food unpredictability). However, the potential combined impact of stressors and methylmercury exposure on avian physiology and seasonal transitions has rarely been studied. To evaluate the impact of methylmercury exposure on songbirds’ physiology and seasonal transitions I worked with song sparrows (Melospiza melodia). Birds were exposed to environmentally relevant doses of methylmercury in combination, or not, with unpredictable food stress and I observed their physiological changes throughout two seasonal transitions: summer to fall and winter to spring. My main finding is that methylmercury delayed moult completion, and increased migratory behaviour in fall. Such effect on migratory behaviour could be due to an increase in corticosterone hormone levels in methylmercury exposed birds. In contrast, the preliminary results of the winter-spring seasonal transition show no treatment effects on brain GnRH producing cells number, blood testosterone levels or testis mass, indicating that spring reproductive onset might not be affected by methylmercury in birds. Overall, my research also highlights the importance of studying contaminant effects over multiple seasons when assessing risk for wildlife.
April 9, 2021
Microplastics have been found throughout aquatic environments and have been reported to impact a number of species. Rivers have been identified to act both as depositional sinks and transport pathways of microplastics to lakes and oceans, however few studies have been conducted in tributaries of the Laurentian Great Lakes system. In addition, limited data are available regarding microplastic ingestion in both riverine and demersal groupings of fish. This study therefore investigated a potential connection between microplastic levels in benthic sediment and ingestion by riverine demersal fish. Building on a previous study of microplastics in benthic sediment from the Thames River, Ontario, demersal fish white sucker along with opportunistic capture of common carp were collected from 11 locations in the Upper Thames River. The gastrointestinal tracts of fishes were digested using 20% KOH and filtered after 48 hours. Microplastics were manually characterized by shape, colour and size, and a subset was analyzed using Fourier Transform Infrared Spectroscopy (FTIR). Results suggest that fishes from urban areas contain a higher number of microplastics, aligning with previous findings regarding urban land use as a contributing source of microplastics to inland waters.
The post-breeding period before fall migration remains an understudied period in the life cycle of migratory birds. The post-breeding period poses significant threats to young newly fledged birds through exploring their new habitat, predation, starvation, or otherwise failing to survive until their first southward migration. To address this gap in knowledge for bank swallows, I will determine survival rates of adult and juvenile bank swallow in the Great Lakes ecoregion. Individuals will be captured using mist nets, banded, have morphological measurements taken, and radio tagged affixed. Detection data will be downloaded from the Motus database. Following Evans et al., (2020), detection data will be converted to encounter histories. Encounter histories will be used to differentiate between lakeshore colony bank swallow and aggregate pit colony bank swallow. Mark-recapture models will be created to estimate post-breeding survival. Models will allow for the comparisons of survival between adults and juveniles and between lakeshore colonies and aggregate pits. Results obtained from this project will help determine if Ontario bank swallow have age dependent post-breeding survival curves and if bank swallow post-breeding survival depends on habitat quality.
March 26, 2021
The rhizosphere, which comprises of the soil that is in direct contact with the roots of a plant, is a hot spot of microbial diversity and dynamic interactions. The rhizosphere has elevated numbers of active microorganisms including plant-beneficial organisms and plant pathogens. The interactions that occur in the rhizosphere can be mutualistic and beneficial to plant growth, with surrounding fungi improving nutrient acquisition and stress tolerance. However, in the rhizosphere are also fungal pathogens that elicit harmful effects on plants, which can result in crop losses. I aim to profile the root and rhizosphere mycobiomes of low and high yield patches of wheat and corn planted in rotation on the same fields by next-generation sequencing of the ITS region. I hope to identify microorganisms providing protective or pathogenic effects for these crops and assess potential correlations between soil and plant health metrics and fungal communities. The knowledge gained through this research can be integrated into current soil health management systems to reduce crop losses.
Humans have been considered “super predators” due to our ability to kill every animal on the planet. In Africa, where prevalent hunting on various large mammals occurs, there is very little experimental literature to document how hunting affects the behaviour of these hunted species. My research objective was to experimentally test whether fear behaviour of a South African mammal community is affected by human presence and hunting. I used a newly developed technology, the Automatic Behavioural Response system, to video record the responses of wildlife to five playback treatments: birdsong, lion snarls, gunshots, dog barks, and human voices. My results show that the majority of the species in the community flee most to the human voice, surpassing their response to both lions and hunting stimuli. However, there was no difference in behaviour between areas of hunting pressure or human presence. These findings demonstrate that not only can humans be more frightening than non-human predators, but also that this fear of us can pervade whole communities of mammals.
March 19, 2021
Plasmids are extrachromosomal replicons that do not share homology to their host genome and have been found to be associated with the mitochondria of many plant, protist, and fungal species as well as with chloroplasts in a few instances. They exist as circular or linear molecules and often contain open reading frames for viral-type DNA and RNA polymerases as well as reverse transcriptases. Although studied extensively in model systems from the 1980s to the early 2000s with the hope of finding useful vesicles for the transformation of genetic products, research in this small sub-field of mitochondrial genomics has halted, despite the exponentially increasing number of genome sequences available. The goal of my project is to data-mine sequence data from GenBank for plasmid-derived sequences and perform evolutionary analysis on a large scale. Mined data can be used to make gene trees and find cases of horizontal gene transfer between species. RNA datasets will be used to find evidence of transcription and to detect the evolution of RNA editing. From this, I hope to widen the understanding of the distribution of plasmid sequences and explain why they are upkept in some species but not others.
Conventional agricultural practices such as deep plowing and the use of chemical fertilizers can reduce both the abundance of beneficial soil invertebrates and their species richness. A declining efficacy of these practices has increased the interest in non-conventional (NC) farming. These includes the use of organic fertilizers, reduced tillage and more extensive rotational cropping, such as the use of cover crops (CCs). Many studies have focused on the benefits of CC-use in relation to crop yield and soil quality. However, very little is known about the responses of beneficial soil fauna to CC use. My study focuses on how different groups of CCs, such as grasses and legumes, influence these soil organisms. It will take place at a NC farm in St. Thomas, ON that practices organic protocols, reduced tillage, and the use of CCs. My research will focus on soil keystone species, such earthworms. Such bioindicators can be used to obtain crucial information regarding changes in the health status of soils in response to CC use.
March 12, 2021
Persistence of a metapopulation and local populations within it are dependent on the dynamic balance between local extinction and recolonization of habitat patches, in which dispersal, the movement and settlement of individuals from their native patch to another, serves as the key mechanism. Despite its importance, the genetic basis of metapopulation-level dispersal is poorly understood, especially in natural systems. In my study, I will utilize the effects of local extinction and removal events on the genetic structure of local populations to characterise a genetic basis of dispersal and recolonization in Parnassius smintheus, an Apollo butterfly species that inhabit meadow patches in the Rocky Mountains. I will be focusing on a metabolism-related candidate locus - Phosphogluclose isomerase (Pgi), that has been associated with variation in movement abilities across several other insect species. I will genotype and assess the change in frequency of single nucleotide polymorphisms (SNP) within the Pgi locus, as well as other SNPs throughout the P. smintheus genome across historical extinction and removal events. I hypothesize that variation in Pgi underlies variation in dispersal in P. smintheus, and therefore predict that variations associated with increased dispersal ability or likelihood will increase in frequency within the local population following recolonization.
March 5, 2021
Animals use migration to find food or suitable habitat for breeding and raising their young. Most North American songbirds are nocturnal migrants with a short-hop migration strategy, meaning they use stopover sites to refuel and build up energetic stores before continuing on their journey of several hours of nocturnal flight. Previous studies have shown that juveniles tend to have longer stopovers and less efficient migratory flight behavior. However, little is known about how age differences can impact songbirds' flight speed. This study focuses on how morphological characteristics influenced by age impact a bird's migration speed. My research will be conducted on black-throated blue warblers at Long Point, Ontario. The birds will be measured, photographed, radio-tagged, and released. Data collected by the Motus Wildlife Tracking System will be used to calculate inter-tower flight speed for different age classes and provide illustrations of the birds' post-departure flight paths. Additionally, GLMs will be used to show sex, age, and different capture dates of birds. This study will provide critical information for piecing together complete migratory journeys in songbirds and help researchers better understand how climate change impacts avian species and how their populations will adapt to these changes to persist into the future.
Most described legumes (family: Fabaceae) form symbioses with nitrogen-fixing rhizobia. These associations increase soil nitrogen inputs, potentially increasing ecosystem fertility. Stressors which affect legumes can therefore impact ecosystem nitrogen dynamics. One common stressor in northern temperate regions is freezing, which can cause mortality or have sub-lethal effects. Herbaceous (i.e., non-woody) species can benefit from snow cover, as it minimizes freezing exposure over winter. Reductions in snow cover, such as those resulting from increased temperature variability, can thus cause plants to experience more severe and frequent freezing. Prior findings suggest herbaceous legumes may be disproportionately susceptible to freezing relative to other functional groups, but these results were based on a limited number of naturally occurring legume species. Using field experimentation with established populations of herbaceous legumes and transplanted legumes and controlled experiments, I have been examining these trends. I have found some but not all herbaceous legume species studied thus far are disproportionately susceptible relative to their non-legume neighbours. These findings suggest that the high freezing susceptibility of herbaceous legumes in northern temperature regions may be a broader phenomenon and may have important implications for changes in ecosystem nitrogen cycling in response to climate change and increased variability in winter conditions.
February 26, 2021
Ginseng is a root plant from the genus (Panax) that is from the family Araliaceae. This plant is used as a traditional herbal medicine in Chinese and Korean culture due to its many medicinal properties. Numerous clinical studies have shown that the major bioactive compound (ginsenosides) holds health benefits towards the body. More importantly, Canada is one of the world’s largest producers with an annual revenue of up to $240 million. Most of the Canadian-grown ginsengs are from Southwestern Ontario, but farmers are currently facing two major problems. Firstly, ginseng replant disease prevents farmers from being able to replant ginseng after it has been grown into gardens. Secondly, farmers are losing suitable lands to grow ginseng, which places a threat on their business. This study is intended to determine how the change in microbiome after the growth of ginseng in new gardens increases the susceptibility to ginseng replant disease for subsequent plantings. Through the use of 16s ribosomal RNA metabarcoding, I will be examining the soil microbiome composition mainly by determining the alpha and beta diversity within soil samples that are collected seasonally from the gardens. In addition, I will also be investigating which taxa or groups of taxa respond similarly throughout ginseng cultivation with network analysis. This work provides insight into the species diversity that are contributing to ginseng replant disease and can potentially be considered as a diagnosis for ginseng farmers in Ontario.
The predatory fish community in Lake Huron is predominantly composed of four salmonids: lake trout (Salvelinus namaycush), Chinook salmon (Oncorhynchus tshawtscha), rainbow trout (O. mykiss), and Coho salmon (O. kisutch). Since 1980 there has been a decline in the biomass of the prey fishes that these salmonids consume. Importantly, one of the most widely consumed prey fish, alewife (Alosa pseudoharengus), suffered a population crash in 2003, imposing a potentially major nutritional stress on Lake Huron’s salmonids. However, little is known about the response of these salmonids to the decreasing prey abundance. My study will compare the diets of salmonids before and after the 2003 alewife crash using stable isotope analysis of archived scale samples collected prior to 2003 and scale samples collected in 2020. Stable isotope analysis will also be conducted on muscle and liver tissue samples to provide a complete timeline of integrated diet between two and four months prior to fish capture. Stomach content analyses (DNA metabarcoding and visual identification) will be further used to provide detailed information about the current diets of these salmonids. Together these data will help quantify the importance of different prey fishes in Lake Huron and support the management of these salmonids.
February 19, 2021
Cadmium-contaminated soils can pose a risk not only to plants but also to consumers. This risk may be reduced by applying selenium, an essential nutrient for animals, which decreases plant cadmium uptake. One possible mechanism of action is through selenium-induced lignification of root cell walls, preventing cadmium from being transported to the shoots. However, where excess sulphate is present, this may not work. Selenium in the form selenate competes with the nutrient sulphate for uptake. Thus, sulphate can interfere with selenate uptake, potentially impacting cadmium uptake. I tested the interactions among cadmium, selenate, and sulphate comparing two species that hyperaccumulate selenium, Astragalus bisulcatus and A. racemosus, and A. canadensis, which takes up much less selenium, along with five crops. Results to date, examining Astragalus spp. found no significant difference in total lignin content of roots in response to selenate. Additionally, increased selenium concentrations were correlated with increased cadmium concentrations across species but trends within species were inconsistent. Additional data on selenium and cadmium concentrations in the crop species is forthcoming. These results will be useful in agronomy, indicating whether selenium biofortification of crops being grown on mildly cadmium-contaminated soil may improve their safety, or if it would be detrimental.
Antibiotic resistance is prolific in the environment. Environmental bacteria have developed diverse genetic mechanisms to resist harmful chemicals (antibiotics) produced by their competitors, and for a century, humans have mass-manufactured these antibiotics to treat bacterial infections. The overconsumption and misuse of antibiotics in healthcare and agriculture, however, has led us into an unprecedented crisis characterized by rising multi-drug resistance in pathogenic bacteria. There is a great need to understand the pathways through which antibiotics enter the environment in order to reduce future interactions between resistant bacteria and humans. The use of biosolids (sewage sludge) as agricultural soil fertilizer is one such pathway, as biosolids frequently contain antibiotics that have carried over from the sewage treatment process. To determine if biosolids could promote antibiotic resistance in soil bacteria, we applied a class of antibiotics commonly found in biosolids to experimental soil microplots for ten years. For my MSc thesis project, I sequenced the 16S ribosomal DNA, gene cassettes (mobile genetic elements known to carry antibiotic resistance genes), and the total environmental DNA within these soil microplots to investigate potential differences in the composition and diversity of bacterial communities, mobile genetic elements, and antibiotic resistance genes, respectively.
February 5, 2021
Global climate warming is expected to intensify, particularly at higher latitudes, in the following decades. In addition, for many northern temperate regions, industrial and agricultural activities have increased over the last century, resulting in high rates of atmospheric nitrogen (N) deposition, with important implications for plant productivity, diversity and global carbon cycling. I am expanding on a pre-existing 15-year-old field experiment to compare the short-term (1-2 year) vs. long term (14-15 year) effects of warming (via overhead heaters) and N fertilizer addition on plant productivity, relative species abundances, and plant tissue N content. Previous results revealed both warming and atmospheric N deposition had additive effects on plant productivity. In my first year of observation, spectral data (normalized difference vegetation index) indicated that the timing of plant green-up was accelerated in warmed plots and both short and long-term N plots. At the peak of vegetation growth (mid-summer), both short term and long-term N treatments increased Poa pratensis biomass, and short-term N addition increased total root biomass. Therefore, contrary to my expectation, the long-term effects did not diverge substantially form the long-term effects, which may be due to the continued persistence of the same dominant grasses at the field site.
Fragmentation, degradation, and loss of suitable habitat paired with climate change have caused declines in species diversity and abundance across the globe, including in butterflies which are important components of many ecosystems. Species re-introduction or translocation is increasingly used as a strategy for restoring biodiversity. Early re-introductions of butterfly species were largely unsuccessful due to a lack of established protocols and insufficient background knowledge. I will develop molecular and genetic tools to inform planned re-introductions an endangered species of butterfly in Ontario, the Mottled Duskywing (Erynnis martialis). My work will form part of a larger, collaborative effort to achieve the overall recovery goal of the species in Ontario and will support a locally-sourced model for insect species at risk recovery planning. Although the Mottled Duskywing is imperiled throughout most of its range, very little published research exists on the species, and no efforts to recover imperiled populations have occurred anywhere in the U.S. or Canada. My work will provide the first information on genetic diversity and structure in this species and will be directly relevant to its conservation and re-introduction in Ontario.
January 29, 2021
As eusocial insects, termites normally maintain kin-based colonies that are closed off to intruders. Termites invasive to urban areas may, however, abandon their colonial life for more inclusive societies that are indifferent to kinship. These large decentralized 'unicolonies' are difficult to eradicate and might arise from a loss of cue diversity upon invasion that hampers their normal ability to distinguish close from distant kin, or to recognize relatives at all. For my PhD, I will perform a series of studies on the locally invasive termite Reticulitermes flavipes that will test this hypothesis on several fronts. First, I will develop behavioral assays that tease apart environmental from genetic factors associated with loss of recognition in urban populations. My anticipated results may help to explain transitions to unicoloniality that are relevant to the pest control industry in Canada and abroad. Second, I will perform an in-depth statistical analysis of urban geographic and socio-economic correlates to termite infestation in Toronto and other Canadian municipalities. Finally, I will develop a comparative sequence analysis pipeline to reveal genetic diversity on a grand scale and possibly reveal genomic signatures of a social insect invasion.
The period between nesting and fall migration, termed post-fledging, is an important and understudied stage for temperate migratory birds. Survival to fall migration for newly fledged independent songbirds becomes more difficult as resources (food and shelter) as well as space are limited. These interactions of resource scarcity and fledgling survival can be observed in habitats where several species are competing for similar finite resources, such as on islands. Georgian Bay, Ontario is a largely untouched area of the Great Lakes ecoregion composed of an abundance of island habitats. These islands provide a unique landscape for breeding and migrating songbirds. Island habitats are separated from the mainland and may impede dispersal between adjacent habitats. The purpose of this research is to understand how avian diversity varies among southeastern Georgian Bay islands in relation to biotic and abiotic factors, and to determine whether movements differ between juvenile and adult songbirds during the postfledging period. Spring breeding bird surveys will be completed on eight (8) islands in southeastern Georgian Bay to identify areas that are actively being used by songbirds. The two (2) islands with the highest songbird breeding density per area will be chosen to capture and attach radio transmitters to focal species individuals. Each island will have 20 juveniles and 20 adult White-throated Sparrows tagged to track their inter and intra island movements. Tagged birds will be tracked using MOTUS towers within and outside of the region as well as daily active tracking methods.
Schedule for the Fall Term 2020
|Seminar Date||First Speaker||Title||Second Speaker||Title|
|16-Apr-21||Carlos Barreto||Global Change Effects on Detrital Food Webs||Claire Bottini||TBA|